Carbon reduction benefits of photovoltaic-green roofs and their climate change mitigation potential: A case study of Xiamen city

The Photovoltaic-Green Roof (PV-GR) system, which integrates rooftop photovoltaics and green roofing, has significant potential for sustainable urban development and climate change mitigation. However, the specific effects of PV-GR are not yet clear. This paper employs methodologies including Geographic Information Systems (GIS), Denitrification-Decomposition(DNDC) Model, and solar simulation. Combined with ecological balance calculations, these methods assess PV-GR's carbon reduction benefits and its potential to mitigate climate change. Using Xiamen City as a case study, research shows that Xiamen has about 54 km² of rooftops suitable for PV-GR. Annually, PV-GR can produce about 5.931×10³ tons of biomass and generate 7,427 GWh of electricity, meeting about 22.13 % of Xiamen's annual electricity demand. The annual carbon reduction from Xiamen's PV-GR is estimated at about 5.131×10⁶ t CO_2-eq, offsetting around 29.28 % of the city's annual carbon emissions. Over a 30-year lifecycle, PV-GR's carbon emissions and reduction benefits amount to 2.274×10⁷ t CO_2-eq and 1.539×10⁸ t CO_2-eq, respectively. The ecological footprint of deploying PV-GR in Xiamen is 6.709×10⁴ Gha, while the biocapacity reaches 4.542×10⁵ Gha. The global ecological balance stands at 3.872×10⁵ Gha, suggesting that PV-GR can significantly contribute to mitigating climate change.